This Element argues that Heidegger's concept of science has two core features. Heidegger critiques a security-oriented concept of science, which he associates with the dominance of physics in modern science and metaphysics and with a progressive resistance among philosophers and scientists to ontological questioning. Meanwhile, Heidegger advances an access-oriented concept of science, on which science is essentially founded on ontological disclosures but also constantly open to the possibility of new revolutionary disclosures. This Element discusses how these commitments develop in Heidegger's early and later thinking, and argues that they inform his views on the history of Western metaphysics and on the possibilities for human flourishing that modernity, and modern science specifically, affords. The Element also discusses Heidegger's dialogue with Werner Heisenberg about quantum physics; and throughout, it highlights points of contact and divergence between Heidegger and other philosophers of science such as Karl Popper, Thomas Kuhn, Paul Feyerabend, and Helen Longino.